Mobile communication devices such as cellular telephones and smart phones including Global Positioning System (“GPS”) receiver functionality often operate poorly in indoor environments with regard to generating precise and accurate location information. For proper operation, GPS receiving devices receive locating signals from GPS satellites, which signals may be blocked by buildings, structures, or other environmental features. Large structures such as malls, office buildings, schools, and parking garages are particularly troublesome, preventing precise and accurate location information from being generated by a mobile device within such structures.
Some mobile device systems are configured to use ground-located cellular base transceiver station signals for computing location, which signals are typically better than GPS signals at penetrating indoor environments. Suitable non-limiting methods for determining location based on base transceiver station signal measurement include but are not limited to: Angle of Arrival (“AOA”), in which the angles of arrival of signals from two base transceiver stations of known position are determined; Time Difference of Arrival (“TDOA”) or Time of Arrival (“TOA”), in which lengths of time it takes to receive signals from three or more base stations of known position are determined; Enhanced Observed Time Difference (“EOTD”), in which lengths of time it takes to receive signals from three or more base stations of known position are determined based on timing data provided via the network; Advanced Forward Link Trilateration (“AFLT”), in which the device position is triangulated based on signal measurements from three or more base stations of known position by determining phase differences of the signals and signal strengths; and signal strength triangulation, in which the device position is triangulated based on signal strength measurements from three or more base stations of known position. Like GPS signals however, signals sent to or received from cellular base transceiver stations may also be impeded by building structures or other environmental features.
It is common for location-based applications and services that depend on GPS and related technologies to include disclaimers that the application or service may not function well when a mobile device from which location information is generated is located indoors. There are currently many location-based applications configured to reside on or enable communication with mobile devices, for example smart phones such as the iPhone™ brand smart phone. Such applications typically only function well if the quality of the location information they rely on is accurate and precise. For example, if execution of a turn-by-turn driving directions application is initiated on a mobile device while the mobile device is in a parking garage shielded from GPS locating signals, the application may not obtain a starting location and therefore cannot begin computing directions for a user.
A user, system, or application which generates a real-time request for a mobile device's location relying on GPS signals, base transceiver station signals, or related systems is likely to obtain poor location data or no useable location data if the mobile device's happens to be indoors at the time of the request. It would be desirable to provide a system for disseminating precise and accurate location information to users, systems, and applications. Such provided system should address inherent deficiencies of GPS or base transceiver station signal reception to provide location information even where reception of signals is impeded.